Commercial and industrial buildings are typically constructed with flat or near flat roofs. Because these buildings do not have much if any of a pitch to the roof, the collection of water on the roof surface resulting from rain and melting snow can present a serious structural load that could result in collapse of the roof's structure. To avoid this possibility most commercial and industrial building standards require that roofs of this type include drains positioned at locations that ensure that at least the majority of water accumulation may be removed from the roof through a drainage plumbing system. These commercial buildings also include various plumbing, heating, ventilation, etc. systems that require venting to the ambient air.
Typical roof drains and vent pipes are installed on flat roofs by cutting a hole through the roof deck and installing a drain therethrough and by cutting another hole through the roof deck and installing a vent pipe or conduit therethrough. The drain typically connects with drainage plumbing that carries the water away and the vent pipe typically connects to the system that requires external venting. The drain and vent structures typically include some form of flashing or collar that, through the application of sealant or other roof material, prevents leakage at the site of the drain installation and at the site of the vent installation. These typical drain and vent structures also include some form of drain ring and under deck clamping ring or structure that holds the drain or the vent in place and prevents its inadvertent removal or dislodgement from its installed position. The opening of the roof drain is typically covered by some form of grating or strainer structure to prevent the ingestion of large objects into the drain plumbing system. In most roof drain structures this strainer or grate takes the form of a hemispherical strainer to prevent or minimize the occurrence of obstruction of the roof drain through the accumulation of leaves and other debris that may accumulate on the roof. The opening of the roof vent may or may not include any grating, but typically does not.
While the usage of roof drains and vent pipes is required for the safety of the roof construction and the proper operation of various systems within the building, such also greatly increases the cost of the roof construction. This significant cost increase is a result of the requirement for the large number of holes through the roof to accommodate the roof drains and vent pipes that must be installed on the roof. Each roof drain and each vent pipe requires a separate deck penetration or hole to be cut in the roof structure. This substantially increases the labor cost associated with such a system as many roof penetrations must be cut. Further, depending on the number of roof drains and vent pipes that are installed, the overall structural strength of the roof may be weakened due to the large number of deck penetrations that are cut to accommodate both the roof drains and the vent pipes.
While these factors may be considered in the design of a new construction, and therefore compensated, the cost and structural impact of installing additional roof drains or additional vent pipes in existing buildings can be prohibitive. That is, on an existing building the roof's structure and strength are already set, and any impact thereto resulting from the installation of the roof drains or vent pipes is not easily compensated. Additionally, the roof surface itself may already be occupied by other equipment that limits the ability to properly position additional roof drains or vent pipes. Further, additional roof penetrations by other systems within a building may also limit the ability to install the roof drains or vent pipes at appropriate locations due to clearance requirements dictated by the roof penetrations of the other systems. As a result, the retrofit of an existing building to install additional roof drains or additional vent pipes often is not only expensive but also quite problematic if they can be installed at all.